The present invention concerns a device for removing condensate from a revolving steam-heated drying cylinder or the like. A condensate standpipe rotates with the drying cylinder, communicates outside by way of a substantially coaxial outlet pipe through a journal of the drying cylinder, and extends up to the inner wall of the cylinder shell where it features a suction mouthpiece. A suction opening forms an inlet group with the inner wall of the cylinder shell, and a condensate guide device is contained in the suction mouthpiece. Devices of this type are preferably used in drying cylinders of the drying section of a paper production machine for the drying of a paper web.
Devices of the this type are known as "rotating syphons". Their configurations offer over the so-called "stationary syphon" the advantage that no relative motion takes place between the revolving drying cylinder and the syphon. Thus, the clearance of the inlet gap between the suction mouthpiece and the inside wall of the cylinder can be kept durably consistent and small by means of spaces. As a result, the condensate layer on the inside wall of the drying cylinder becomes permanently thin, resulting in a good heat transfer from the steam to the surface of the drying cylinder under all operating conditions.
Different configurations are known for "rotating syphons", specifically with respect of the suction mouthpiece which is opposite the inside wall of the cylinder shell.
Known from the German Patent Disclosure 35 35 315, corresponding to U.S. Pat. No. 4,718,177, is a rotating syphon where the suction mouthpiece is coordinated with an additional side channel which is fashioned as a steam blow line serving to counteract flooding of the drying cylinder.
Known from U.S. Pat. No. 3,034,225 is a suction mouthpiece in the form of a dish, and from U.S. Pat. No. 2,993,282 one that has the shape of a bell. U.S. Pat. No. 2,892,264 shows a suction mouthpiece with a funnel-shaped suction snout that opens in the orbital direction; the suction mouthpiece itself is attached to the end of a semicircular condensate standpipe whose end supporting the suction mouthpiece extends approximately coaxial with the inside wall of the cylinder shell. Known from U.S. Pat. No. 3,264,754, lastly, is a suction mouthpiece having the shape of a flat nozzle whose slot-shaped inlet opening extends parallel to the direction of rotation and in the inlet area of which there are bevels provided which in the axially parallel direction slant toward the inside wall of the cylinder shell favoring the influx of condensate. An insert of similar effect and having the shape of a partition for reversing the condensate into the interior of the suction mouthpiece is also taught by said U.S. Pat. No. 2,993,282. According to U.S. Pat. No. 4,384,412, the cross section of the partition is wedge-shaped in order to improve said reversal effect.
The objective of these designs is to increase the transport effect of the steam on the condensate and thus the conveying capacity in the condensate standpipe. This transport effect, in principle, is based on the fact that inside the drying cylinder a higher steam pressure is present than in the condensate standpipe including the suction mouthpiece, so that a part of the steam supplied from outside constantly flows outward through the rotating syphon, mixes with the amount of condensate to be conveyed and thus removes it outward.
Based on the specific design of the suction mouthpiece and, as the case may be, on the arrangement of additional steam holes, these prior conceptions or designs have by and large proved and established themselves in practice. It has so far been accepted that the quantities of steam that are required for a dependable dewatering of the cylinder interior are very large, due to the necessary and relatively high differential pressure between cylinder interior and condensate standpipe.